DB code: S00533

RLCP classification	1.30.36211.1000 : Hydrolysis
CATH domain	2.60.120.180 : Jelly Rolls	Catalytic domain
E.C.	3.2.1.4
CSA
M-CSA
MACiE

CATH domain	Related DB codes (homologues)
2.60.120.180 : Jelly Rolls	S00150 S00151 D00504 D00538

Uniprot Enzyme Name
UniprotKB	Protein name	Synonyms	CAZy	Pfam
O74705		Endoglucanase A EC 3.2.1.4	GH12 (Glycoside Hydrolase Family 12)	PF01670 (Glyco_hydro_12) [Graphical View]

KEGG enzyme name
cellulase endo-1,4-beta-D-glucanase beta-1,4-glucanase beta-1,4-endoglucan hydrolase celluase A cellulosin AP endoglucanase D alkali cellulase cellulase A 3 celludextrinase 9.5 cellulase avicelase pancellase SS 1,4-(1,3 1,4)-beta-D-glucan 4-glucanohydrolase

UniprotKB: Accession Number	Entry name	Activity	Subunit	Subcellular location	Cofactor
O74705	O74705_ASPNG

KEGG Pathways
Map code	Pathways	E.C.
MAP00500	Starch and sucrose metabolism

Compound table
	Substrates				Products		Intermediates
KEGG-id	C00760	C00478	C00551	C00001	C00760	C00551
E.C.
Compound	Cellulose	Lichenin	beta-D-Glucan	H2O	Cellulose	beta-D-Glucan	Transition-state for glycosylated enzyme	Glycosylated enzyme intermediate
Type	polysaccharide	carbohydrate	polysaccharide	H2O	polysaccharide	polysaccharide
ChEBI				15377 15377
PubChem		439241 439241	46173706 46173706	22247451 962 22247451 962		46173706 46173706

1ks4A	Unbound	Unbound	Unbound		Unbound	Unbound
1ks5A	Unbound	Unbound	Unbound		Unbound	Unbound

Reference for Active-site residues
resource	references	E.C.
PDB;1h8v, literature [2], [4]

Active-site residues
PDB	Catalytic residues	Cofactor-binding residues	Modified residues	Main-chain involved in catalysis	Comment

1ks4A	ASP 95;ASP 99;GLU 116;GLU 204
1ks5A	ASP 95;ASP 99;GLU 116;GLU 204

References for Catalytic Mechanism
References	Sections	No. of steps in catalysis
[1]	p.663-664

References
[1]
Resource
Comments	X-RAY CRYSTALLOGRAPHY (2.1 ANGSTROMS) OF 17-239.
Medline ID
PubMed ID	11914491
Journal	Acta Crystallogr D Biol Crystallogr
Year	2002
Volume	58
Pages	660-7
Authors	Khademi S, Zhang D, Swanson SM, Wartenberg A, Witte K, Meyer EF
Title	Determination of the structure of an endoglucanase from Aspergillus niger and its mode of inhibition by palladium chloride.
Related PDB	1ks4 1ks5
Related UniProtKB	O74705

Comments
This family belongs to glycosidase family-12, which has a retaining mechanism. The catalytic domain of this enzyme is homologous to those of another cellulase (S00150 in EzCatDB) and beta-1,4-Glucanase (D00504 in EzCatDB), whose catalytic mechanisms must be similar to that of this enzyme. According to the literature [1], the catalytic reaction proceeds as follows: (1) Asp95 may modulate the activity of Glu204 as a acid-base. (2) Glu204 acts as a general acid to protonate the leaving oxygen atom, leading to a oxocarbenium-like transtion state from cellulose substrate. (3) pKa of Glu116, which acts as a nucleophile, is modulated by Asp99. (4) Glu116 makes a nucleophilic attack on C1 atom of the transition state, forming a glycosyl-enzyme intermediate. (5) Glu204 acts as a general base to activate a water molecule. (6) The activated water makes a nucleophilic attack on the C1 atom of the intermediate. This reaction proceeds through an oxocarbenium-like transition state to complete the hydrolysis.

Comments

This family belongs to glycosidase family-12, which has a retaining mechanism.
The catalytic domain of this enzyme is homologous to those of another cellulase (S00150 in EzCatDB) and beta-1,4-Glucanase (D00504 in EzCatDB), whose catalytic mechanisms must be similar to that of this enzyme.
According to the literature [1], the catalytic reaction proceeds as follows:
(1) Asp95 may modulate the activity of Glu204 as a acid-base.
(2) Glu204 acts as a general acid to protonate the leaving oxygen atom, leading to a oxocarbenium-like transtion state from cellulose substrate.
(3) pKa of Glu116, which acts as a nucleophile, is modulated by Asp99.
(4) Glu116 makes a nucleophilic attack on C1 atom of the transition state, forming a glycosyl-enzyme intermediate.
(5) Glu204 acts as a general base to activate a water molecule.
(6) The activated water makes a nucleophilic attack on the C1 atom of the intermediate. This reaction proceeds through an oxocarbenium-like transition state to complete the hydrolysis.

Created	Updated
2004-05-17	2009-02-26